In order to achieve a reduction in automobile fuel consumption, there is a demand for the sidewall portion of a pneumatic tire to have excellent low heat build-up when formed into a tire.
Under such circumstances, a rubber composition for a tire sidewall containing a natural rubber, a butadiene rubber, and a carbon black having a specific nitrogen adsorption specific surface area is disclosed in Patent Document 1 (scope of the patent claims, working examples, and the like). It is described in Patent Document 1 that tan δ is reduced and fuel consumption is improved by the configuration disclosed in Patent Document 1.